Heretofore in the manufacture of hoses, such as rubber hoses, the outer layer of such, when not protected as before vulcanization thereof, was readily deformable and easily marked. During vulcanization, deformity was also caused by the weight of the hose itself and also when layers of a coiled hose were placed upon one another. Damage from scuffing as well as from imperfections in a pan also occurred when the hose was placed in a vulcanizing pan. A clean and smooth hose surface is desired for a final product.
The prior art has attempted to overcome some of the above disadvantages by providing a removable, protecting hose covering which remained thereon during vulcanization. Typically, such covering was made of lead. However, due to the fact that lead is heavy, not flexible, expensive, and poses EPA problems, it has many drawbacks.
In U.S. Pat. No. 3,255,284, a nylon sheath was extruded over the hose prior to vulcanization and remained thereon during vulcanization. However, nylon is slow in extruding, relatively stiff, can be reused only a limited number of times, and is highly sensitive to moisture.
U.S. Pat. No. 3,883,384 relates to a protective sheath of a non-vulcanizable rubber-like material such as EPDM, that is a terpolymer of ethylene, propylene, and a diene; EPM, a copolymer of ethylene and propylene; or CSE, that is chlorosulfonyl-polyethylene. Although such materials have been utilized, they are not desirable since the ability to be removed from a vulcanized hose and recycled is limited. Moreover, the above prior art patents fail to teach or suggest the utilization of a microwave transparent thermoplastic material.
U.S. Pat. No. 4,379,011 merely relates to a method of making arched V-Belts and does not utilize any protective sheath or suggest microwave curing.
U.S. Pat. No. 4,378,622 relates to a method of making a compressible printing roller wherein a microporous inner layer exists. A cover 16 exists about said microporous layer.
U.S. Pat. No. 4,130,535 relates to blends of olefin rubber and thermoplastic olefin resin in which the rubber is completely cured.
U.S. Pat. No. 4,311,628 relates to a similar blend which is cured with a phenolic curative.
U.S. Pat. No. 4,380,606 relates to a blend of a neutralized acrylic copolymer rubber and polyvinylchloride.
The above prior art patents all lack any suggestion of a thermoplastic jacket to protect, smooth and compact the hose composition undergoing vulcanization as by a microwave curing process.